Centrifugal governor for a motion picture camera



0d. 9, 1934. I J. STQIBER 1,976,304

CENTRIFUGAL GOVERNOR FOR A MOTION PICTURE CAMERA Filed June 50, 1932JasgphSiviber,

" w fg Patented Oct. 9, 1934 UNITED TES PATENT OFFICE Joseph Stoiber,Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., acorporation of New York Application June 30, 1932, Serial No. 620,189

3 Claims.

The present invention relates to a centrifugal governor and moreparticularly to a governor for use on high speed motion picture cameras.

The use of multiple speed centrifugal governors on high speed cameras tovary the speed of camera operation is known. However, the weights in theordinary type of centrifugal governor are only slightly displaced at lowspeeds so that the graduations for setting the governor are crowded orclose together over the range of low speeds.

The primary object of the present invention is the provision of acentrifugal governor in which increasing resilient resistance is offeredto displacement of the weights by the centrifugal forces in the governorso that the graduations for the various governor speeds are not crowdedtogether for the low speed settings.

Other objects of the present invention will be suggested to thoseskilled in the art as the disclosure of my invention is continuedhereinafter.

The above and other objects of the invention are attained by theprovision in a centrifugal governor of a spring means which presentscomparatively little resistance to displacement of the governor weightsat low speeds and which presents comparatively high resistance todisplacement of the governor weights at high speeds. Such a spring meansis preferably composed of two portions of different characteristics, theweaker portion controlling the displacements of the governor weights atlow speeds and the stronger portion controlling the displacements of theweights at high speeds. Alternatively, the spring means may have atapering or increasing cross section so that the spring convolutions ofsmall cross section are weak and result in more even distribution of thegovernor settings over the low speed range.

Reference is hereby made to the accompanying drawing in the severalfigures of which similar reference numerals designate similar elements,and in which:

Fig. 1 is a graphical illustration of the operating characteristics ofthe spring means according to the invention as compared to thecharacteristics of spring means of known form.

Fig. 2 is a plan View of a centrifugal governor according to theinvention and means for setting the governor speed.

Fig. 3 is a plan view of the centrifugal governor shown in Fig. 1 butillustrating that the weaker of the two springs is entirely overcome byaxial displacement of the weight members before the stronger spring isappreciably compressed.

Fig. 4 is a side elevation of Fig. 2 illustrating the spacing of thespeed settings on the casing.

Fig. 5 is a plan view of a centrifugal governor having a modified formof spring means which in this case has a tapering cross section so thatthe convolutions of the spring are successively overcome by displacementof the governor weights.

As previously indicated, it has not been possible heretofore toconstruct a centrifugal governor for motion picture cameras such thatthe low speed settings of the governor are not crowded together. As aresult, the low speed settings of the governor are very apt to beinaccurate and such inaccuracy is quite undesirable, especially at lowspeeds at which any discrepancy in the speed setting will be morenoticeable. I

Referring to Fig. l, the line A graphically illustrates the settings atthe various speeds for the ordinary type of centrifugal governor. Itwill be noted that the lower speeds, namely 8 and 16 frames per second,are close together. The range of governor weight displacements may beincreased by using a weaker spring and this is graphically illustratedby the line B in which the entire displacement over the complete speedrange is more than twice that of line A. However, the displacements forthe low speed settings have not been spread out and are stillobjectionably close together. The present invention consists inproviding a governor spring which ofiers increased resilient resistanceto the displacement of the governor weights as the governor speedincreases. comparatively small resilient resistance is presented to thedisplacements at low speeds and the seetings for these speeds are spreadout as graphically illustrated by the line C of Fig. 1. These graphicalillustrations are all based upon the results of actual tests.

Referring now to Figs. 2, 3, and 5 of the drawing, the centrifugalgovernor is mounted between the camera mechanism plates 10 and 11. Ashaft 12 is rotatably mounted at each end in plates 10 and 11. A collar13 is fixed to shaft 12 by a pin 14 and shaft 12 is rotated by anysuitable prime mover through a gear 15, also fastened to shaft 12adjacent collar 13. A slidable collar 16 is keyed to shaft 12 to turntherewith but adapted to slide axially thereon and has a pin 1'7engaging a slot 18 in shaft 12. A governor disk 19 is attached to collar16 to rotate with shaft 12 but axially slidable with respect thereto. Aplurality of weight members 20 are movably mounted between collars 13and 16 by means of a plurality of links 21. The governor constructionthus far described and the axial displacement of governor disk 19 uponrotation of shaft 12 by virtue of the centrifugal forces created inweight members 20, are well known. However, the present practicerecognizes only the use of an ordinary coil spring to oppose theapproach of collars 13 and 16 toward each other but, as pointed out,this results in crowd ing of the low speed settings.

In the preferred form of my invention, the spring means which opposesthe displacement of slidable collar 16 and governor disk 19 under theaction of weight members 20, is composed of two portions havingdissimilar resilient characteristics. One portion of the spring meansmay be a light coil spring 22 which may encircle shaft 12 adjacentslidable collar 16 while the other portion of the spring means may be aheavy coil spring 23 which encircles shaft 12 adjacent collar 13. Awasher 24 encircles shaft 12 and is located between light coil spring 22and heavy coil spring 23.

The light coil spring 22 is overcome first by axial displacement ofcollar 16 and has its ultimate resilient resistance under compressionproportioned to the ultimate resilient resistance of heavy coil spring23 so that rotation of the governor shaft 12 at normal speed will resultin complete compression of light coil spring 22. The normal speedreferred to is the usual speed at which amateur motion picture camerasare operated, that is 16 frames or pictures per second. The relation ofthe parts at this normal speed, and with the light coil spring 22completely compressed, is illustrated in Fig. 2. Increase in therotative speed of shaft 12 beyond the normal speed will result incompression of the heavy coil spring 23.

A modified form of thespring means according to the invention isillustrated in Fig. 5. The spring means in this case is a coil spring 25having tapering characteristics; that is, the spring is made up in theusual manner and then ground down to a taper while compressed. The coilspring 25 may, of course, be replaced by any other spring of similarcharacteristics, such as a spring which has been coiled from a graduallytapering wire. The increased resilient resistance of coil spring 25 isattained more gradually than with the pair of springs 22 and 23 becausethe single convolutions of spring 25 are overcome upon displacement ofcollar 16 successively and one at a time. The portion of the parts inFig. 5 illustrates the displacement of collar 16 and governor disk 19 atnormal speeds and at which some of the spring convolutions abut eachother, leaving only the stronger convolutions of the spring to opposefurther increase in the governor speed.

A brake means for limiting the displacement of collar 16 and governordisk 19 by weights 20 under the influence of centrifugal force will nextbe described. Such a brake means may include a brake arm 26 pivotallymounted upon a bracket 2'7 which is attached to mechanism plate 11. Abrake shoe 28 is mounted upon the free end of brake arm 26 and may becomposed of leather, cork, or other suitable material.

An adjustable stop means for controlling the position of the brake arm26 is composed of a threaded stem 29 having a head piece 30 attached toone end and a dial 31 attached to the other end, the threaded stem 29engaging a split nut 32 mounted on mechanism plate 10. The head piece 30is attached to and may be adjustably located on the end of threaded stem29 by means of a pair of set screws 32. The head piece 30 abuts brakearm 26 and a spring 33 holds brake arm 26 against head piece 30 in allpositions thereof.

The face of dial 31 extends into an opening in the camera casing 34 anda knurled, annular ridge 35 is provided on the face of dial 31 tofacilitate manual rotation thereof.

Referring now to Fig. 4, the camera casing 34 is provided with aplurality of graduations 36 adapted to register with an index mark 37 ontheface of dial 31 to indicate the various settings of head piece 30 forcorresponding governor speeds. Numerals indicating the exposures persecond at which the camera is operating are etched upon camera casing 34adjacent the appropriate graduations 36. A lug 38 on mechanism plate 10cooperates with a projection 39 on dial 31 to prevent more than a singlerotation of dial 31.

The operation of the centrifugal governor according to the inventionwill now be described. Assuming that dial 31 is set in the positionshown in Fig. 4 with index mark 37 opposite the graduation 36 for normaloperation of the camera at 16 exposures per second, then brake arm 26will abut head piece 30 with brake shoe 28 in the position shown in Fig.2. As the shaft 12 comes up to speed, the centrifugal forces in weightmembers 20 will cause them to fly away from the shaft and will result inaxial movement of slidable collar 16 toward collar 13. The spring meansof the governor will be compressed, the resilient resistance of theweaker portion or weaker convolutions of the spring means being firstovercome. Since the shaft 12 is preferable driven by a spring motor, thespeed of rotation thereof will continue to increase until governor disk19 rubs against brake shoe 28, which prevents further axial displacementof disk 19 and which prevents further increase in the speed of shaft 12.If the setting of dial 31 is altered, then the position of brake shoe 28will be correspondingly changed and the displacement of governor disk 19will be limited to that which corresponds to the speed of rotationdesired.

Since many modifications of my invention may be made without exceedingthe scope of the invention, the present disclosure is to be construed inan illustrative and not in a limiting sense.

Having now particularly described my invention what I desire to secureby Letters Patent of the United States and what I claim is:

1. A motionv picture apparatus for operating over a speed range of whichthe highest speed is many times the lowest speed, comprising a casingprovided with an opening, a centrifugal governor including a pluralityof weights mounted for rotation about an axis, including a disk axiallymovable by the action of said weights, and including a resilient meansacting in opposition to axial movement of said disk, a brake membermovable to various positions and adapted in each of said positions tolimit the axial movement of said disk and to limit the rotational speedof said governor, an adjustable means for controlling the location ofsaid brake member in said various positions, and a plurality ofgraduations and an index arranged on said casing and said adjustablemeans for relative movement and adapted to indicate the governor speedscorresponding to said various positions of said brake member,characterized by said resilient means including a plurality of springconvolutions having different resilient resistances and acting at alltimes simultaneously to present increasing resistance at an increasingrate to said axial movement of said disk as the governor speeds increasefrom said lowest to said highest speeds.

2. A motion picture apparatus for operating over a speed range of whichthe highest speed is many times the lowest speed, comprising a casingprovided with an opening, a centrifugal governor including a pluralityof weights mounted for rotation about an axis, including a disk axiallymovable by the action of said weights, and including a resilient meansacting in opposition to axial movement of said disk, a brake membermovable to various positions and adapted in each of said positions tolimit the axial movement of said disk and to limit the rotational speedof said governor, an adjustable means for controlling the location ofsaid brake member in said various positions, and a plurality ofgraduations and an index arranged on said casing and said adjustablemeans for relative movement and adapted to indicate the governor speedscorresponding to said various positions of said brake member,characterized by said resilient means including a plurality of springsof different strengths and located in end to end relation to present anincreasing resistance at an increasing rate to said axial movement ofsaid disk as the governor speeds increase from said lowest to saidhighest speeds.

3. A motion picture apparatus for operating over a speed range of whichthe highest speed is many times the lowest speed, comprising a casingprovided with an opening, a centrifugal governor including a pluralityof weights mounted for rotation about an axis, including a disk, axiallymovable by the action of said weights, and including a resilient meansacting in opposition to axial movement of said disk, a brake membermovable to various positions and adapted in each of said positions tolimit the axial movement of said disk and to limit the rotational speedof said governor, an adjustable means for controlling the location ofsaid brake member in said various positions, and a plurality ofgraduations and an index arranged on said casing and said adjustablemeans for relative movement and adapted to indicate the governor speedscorresponding to said various positions of said brake member,characterized by said resilient means including a conical spring havingconvolutions of increasing resilient resistances and presenting rapidlyincreasing resistance at an increasing rate to said axial movement ofsaid disk as the governor speeds increase from said lowest to saidhighest speeds.

JOSEPH STOIBER.

